The metabolism of bile pigments in fetal and neonatal monkeys will be investigated. Particular emphasis will be placed on the enterohepatic circulation of bilirubin and its derivatives. The chemical structure and metabolism of pigments found in the gall bladder, meconium, intestinal wall, portal vein, intestinal lymphatics, urine and amniotic fluid will be studied. These pigments will be studied by biochemical methods including spectrophotometry, paper chromatography and thin layer chromatography, and by studies with radioactive isotopes.